Prokl - Penguin Rolling on Keyboard Laughing.
May be used, say, in a conversation where the other member screams AHHH CAT ON KEYBOARD!! )@#$%)$%)!@)!@#)$!@#$ (With a trail of garbled characters as the cat steps across the keyboard) <There is no known explanation as to WHY cats love the keyboard...>
Anyway, it works especially well if you're a known linux user, in which case 'penguin' becomes more symbolic. See Example: